Low-pressure nitrogen turbine with air booster parallel to the booster air compressor

ABSTRACT

An air separation process having a first booster air compressor comprising a first outlet stream and a second booster air compressor comprising a second outlet stream. Wherein the first booster air compressor and the second booster air compressor are in parallel, and the second booster air compressor is driven by a nitrogen turboexpander. The first outlet stream and/or the second outlet stream may be at least partially condensed by heat exchange with a vaporizing low pressure oxygen stream, and the low-pressure gaseous oxygen pressure is in the range of 1.1 bara to 3 bara.

BACKGROUND

A system as known in the art is presented in FIGS. 1 through 4 . A main air compressor (not shown) compresses air to provide feed air stream 101 which is split into main feed air stream 102 and secondary feed air stream 103. Main feed air stream 102 is introduced into main heat exchanger 104 wherein it is cooled, thereby producing cold feed air stream 105. Secondary feed air stream 103 is introduced into first booster air compressor 106 thereby producing boosted air feed stream 107. Secondary feed air stream 103 has a first inlet pressure, and boosted air feed stream 107 has a first outlet pressure. Boosted air feed stream 107 is introduced into aftercooler 108, thereby producing cooled compressed air feed stream 109. The pressure of cooled compressed air feed stream 109 is determined by the oxygen vaporizing pressure in first heat exchanger 203. For efficient heat transfer the air condensing temperature in first heat exchanger 203 must be only slightly (˜2 C to 3 C) warmer than the temperature of the vaporizing oxygen. Cooled compressed air feed stream 109 is then introduced into main heat exchanger 104 wherein it is cooled, thereby producing cool boosted feed air stream 110,

Cold feed air stream 105 is introduced into HP column 201. Cool boosted feed air stream 110 is introduced into first heat exchanger 203, wherein it exchanges heat with liquid oxygen stream 214, thereby producing at least partially condensed cold boosted feed air stream 204. Second heat exchanger 203 vaporizes liquid oxygen stream 214 against at least partially condensing air stream 110 at a pressure provided by first booster air compressor 106. The pressure of liquid oxygen stream 214 vaporized in second heat exchanger 203 is boosted by static head by positioning second heat exchanger 203 at a lower elevation than the liquid oxygen supply sump 217 of LP column 202. Alternatively, the pressure of liquid oxygen stream 214 may be boosted by a liquid oxygen pump. (not shown). For this process the gaseous oxygen product pressure is in the range of 1.1 bara to 3 bara and preferably in the range of 1.2 bara and 2 bara.

Cold boosted feed air stream 204 may be split into two portions, primary cold boosted feed air stream 205 and secondary cold boosted fed air stream 206. Primary cold boosted feed air stream 205 is introduced into HP column 201. Secondary cold boosted fed air stream 206 is introduced into LP column 202.

In one embodiment, as illustrated in FIG. 1 and FIG. 2 , HP column 201 produces at least four output streams, rich liquid stream 208, first nitrogen reflux stream 210, second nitrogen reflux stream 212, and HP gaseous nitrogen stream 117, Rich liquid stream 208 passes through second heat exchanger 207, thereby producing cold rich liquid stream 209, which is introduced into LP column 202. First nitrogen reflux stream 210 passes through second heat exchanger 207, thereby producing cold first reflux stream 211, which is introduced into LP column 202. Second nitrogen reflux stream 212 passes through second heat exchanger 207, thereby producing cold second reflux stream 213, which is introduced into LP column 202.

LP column 202 produces at least three output streams, liquid oxygen stream 214, cold waste nitrogen stream 215, and cold gaseous nitrogen stream 216. Liquid oxygen stream 214 passes through first heat exchanger 203, thereby producing gaseous oxygen product stream 115. Gaseous oxygen product stream 115 may have a pressure between 1.1 and 3 bara, preferably between 1.2 and 2 bara. Cold waste nitrogen stream 215 passes through second heat exchanger 207, thereby producing waste nitrogen stream 113. Cold gaseous nitrogen stream 216 passes through second heat exchanger 207, thereby producing gaseous nitrogen product stream 111.

Gaseous nitrogen product stream 111 is introduced into main heat exchanger 104, thereby producing warmed gaseous nitrogen product 112. Waste nitrogen product stream 113 is introduced into main heat exchanger 104, thereby producing warmed waste nitrogen product 114. Gaseous oxygen product stream 115 is introduced into main heat exchanger 104, thereby producing warmed gaseous oxygen product 116.

HP gaseous nitrogen stream 117 is introduced into main heat exchanger 104, thereby producing warmed HP gaseous nitrogen stream 118. Warmed HP gaseous nitrogen stream 118 is then introduced into turboexpander 119, thereby producing LP gaseous nitrogen stream 120. Turboexpander 119 may have an inlet pressure of between 4 and 10 bara, and an outlet pressure of between atmospheric pressure and 2 bara. Turboexpander 119 may have a loading or braking device to act as a sink for the expander's energy. As a brake, turboexpander 119 may utilize a booster, a generator or oil (not shown). Typically, a booster brake is preferred to put as much energy back into the system as possible, with less overall losses and equipment cost. LP gaseous nitrogen stream 120 is then introduced into main heat exchanger 104 thereby producing warmed LP gaseous nitrogen stream 121.

In another embodiment, as illustrated in FIG. 3 and FIG. 4 , HP column 201 produces at least 3 output streams rich liquid stream 208, nitrogen reflux stream 212, and HP gaseous nitrogen stream 117. Rich liquid stream 208 passes through second heat exchanger 207, thereby producing cold rich liquid stream 209, which is introduced into LP column 202. Nitrogen reflux stream 212 passes through second heat exchanger 207, thereby producing cold reflux stream 213, which is introduced into LP column 202.

LP column 202 produces at least two output streams, liquid oxygen stream 214, cold waste nitrogen stream 215, Liquid oxygen stream 214 passes through first heat exchanger 203, thereby producing gaseous oxygen product stream 115. Gaseous oxygen product stream 115 may have a pressure between 1.1 and 3 bara, preferably between 1.2 and 2 bara. Cold waste nitrogen stream 215 passes through second heat exchanger 207, thereby producing waste nitrogen stream 113. Waste nitrogen product stream 113 is introduced into main heat exchanger 104, thereby producing warmed waste nitrogen product 114. Gaseous oxygen product stream 115 is introduced into main heat exchanger 104, thereby producing warmed gaseous oxygen product 116.

HP gaseous nitrogen stream 117 is introduced into main heat exchanger 104, thereby producing warmed HP gaseous nitrogen stream 118. Warmed HP gaseous nitrogen stream 118 is then introduced into turboexpander 119, thereby producing LP gaseous nitrogen stream 120. Turboexpander 119 may have an inlet pressure of between 4 and 10 bara, and an outlet pressure of between atmospheric pressure and 2 bara, Turboexpander 119 may have a loading or braking device to act as a sink for the expander's energy. As a brake, turboexpander 119 may utilize a booster, a generator or oil (not shown). Typically, a booster brake is preferred to put as much energy back into the system as possible, with less overall losses and equipment cost. LP gaseous nitrogen stream 120 is then introduced into main heat exchanger 104 thereby producing warmed LP gaseous nitrogen stream 121.

SUMMARY

An air separation process having a first booster air compressor comprising a first outlet stream and a second booster air compressor comprising a second outlet stream, Wherein the first booster air compressor and the second booster air compressor are in parallel, and the second booster air compressor is driven by a nitrogen turboexpander. The first outlet stream and/or the second outlet stream may be at least partially condensed by heat exchange with a vaporizing low pressure oxygen stream, and the low-pressure gaseous oxygen pressure is in the range of 1.1 bara to 3.1 bara.

BRIEF DESCRIPTION OF THE FIGURES

For a further understanding of the nature and objects for the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements are given the same or analogous reference numbers and wherein;

FIG. 1 is a schematic representation of the main heat exchanger with a low-pressure nitrogen stream, as utilized in one system as known in the art,

FIG. 2 is a schematic representation of an overall system with a low-pressure nitrogen stream, as utilized in one system as known in the art.

FIG. 3 is a schematic representation of the main heat exchanger without a low-pressure nitrogen stream, as utilized in one system as known in the art.

FIG. 4 is a schematic representation of an overall system without a low-pressure nitrogen stream, as utilized in one system as known in the art.

FIG. 5 is a schematic representation of the main heat exchanger with a low-pressure nitrogen stream, in accordance with the present invention.

FIG. 6 is a schematic representation of an overall system with a low-pressure nitrogen stream, in accordance with the present invention.

FIG. 7 is a schematic representation of the main heat exchanger without a low-pressure nitrogen stream, in accordance with the present invention.

FIG. 8 is a schematic representation of an overall system without a low-pressure nitrogen stream, in accordance with the present invention.

ELEMENT NUMBERS

101=feed air stream

102=main feed air stream (first portion)

103=secondary feed air stream (second portion)

104=main heat exchanger

105=cold feed air stream

106=first booster air compressor

107=boosted air feed stream

108=aftercooler

109=cooled compressed air feed stream

110=cool boosted feed air stream

111=gaseous nitrogen product

112=warmed gaseous nitrogen product

113=waste nitrogen

114=warmed waste nitrogen

115=gaseous oxygen product

116=warmed gaseous oxygen product

117=HP gaseous nitrogen

118=warmed HP gaseous nitrogen

119=turboexpander

120=LP gaseous nitrogen

121=warmed LP gaseous nitrogen

201=HP column

202=LP column

203=first heat exchanger

204=cold boosted feed air stream

205=primary cold boosted feed air stream (first portion)

206=secondary cold boosted feed air stream (second portion)

207=second heat exchanger

208=rich liquid (rich in oxygen)

209=cold rich liquid

210=first (nitrogen) reflux stream

211=cold first reflux stream

212=second (nitrogen) reflux stream

213=cold second reflux stream

214=gaseous oxygen stream

215=cold waste nitrogen stream

216=cold gaseous nitrogen

301=tertiary feed air stream (third portion)

302=second booster air compressor

303=drive connection (between turboexpander and secondary feed air compressor)

304=compressed tertiary feed air stream

305=combined boosted feed air stream

DESCRIPTION OF PREFERRED EMBODIMENTS

Illustrative embodiments of the invention are described below. While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims,

It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer's specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another, Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

Turning to FIGS. 5 through 8 , a system in accordance with the present invention is presented. A main air compressor (not shown) compresses air to provide feed air stream 101 which is split into main feed air stream 102 and secondary feed air stream 103, and tertiary feed air stream 301. Main feed air stream 102 is introduced into main heat exchanger 104 wherein it is cooled, thereby producing cold feed air stream 105. Secondary feed air stream 103 is introduced into first booster air compressor 106 thereby producing boosted air feed stream 107. Secondary feed air stream 103 has a first inlet pressure, and boosted air feed stream 107 has a first outlet pressure, Tertiary feed air stream 301 is introduced into second booster air compressor 302, thereby producing compressed tertiary feed air stream 304. Tertiary feed air stream 301 has a second inlet pressure and compressed tertiary feed air stream 304 has a second outlet pressure. The first inlet pressure and the second inlet pressure are the same, which is defined herein as being within 1 bar of each other, The first outlet pressure and the second outlet pressure are the same, which is defined herein as being within 1 bar of each other.

Boosted air feed stream 107 is combined with compressed tertiary feed air stream 304, thereby producing combined boosted feed air stream 305. Thus, first booster air compressor 106 and second booster air compressor 302 are in parallel, having the same, or approximately the same, inlet pressures and outlet pressures. The term “the same, or approximately the same” means as close to the same as is reasonable given the conditions. As used herein, the term “the same, or approximately the same” is defined as being within 5 bara, preferably within 1 bara of each other.

First booster air compressor 106, may control this common discharge pressure, in order to fully vaporize the oxygen stream. The load on turboexpander 119 will determine the relative flowrates between first booster air compressor 106 and second booster air compressor 302. Combined boosted feed air stream 305 is introduced into aftercooler 108, thereby producing cooled compressed air feed stream 109. Cooled compressed air feed stream 109 is then introduced into main heat exchanger 104 wherein it is cooled, thereby producing cool boosted feed air stream 110.

Cold feed air stream 105 is introduced into HP column 201. Cool boosted feed air stream 110 is introduced into first heat exchanger 203, wherein it exchanges heat with liquid oxygen stream 214, thereby producing at least partially condensed cold boosted feed air stream 204. Cold boosted feed air stream 204 is split into two portions, primary cold boosted feed air stream 205 and secondary cold boosted fed air stream 206. Primary cold boosted feed air stream 205 is introduced into HP column 201. Secondary cold boosted fed air stream 206 is introduced into LP column 202.

In one embodiment, as illustrated in FIG. 5 and FIG. 6 , HP column 201 produces at least four output streams, rich liquid stream 208, first nitrogen reflux stream 210, second nitrogen reflux stream 212, and HP gaseous nitrogen stream 117, Rich liquid stream 208 passes through second heat exchanger 207, thereby producing cold rich liquid stream 209, which is introduced into LP column 202. First nitrogen reflux stream 210 passes through second heat exchanger 207, thereby producing cold first reflux stream 211, which is introduced into LP column 202. Second nitrogen reflux stream 212 passes through second heat exchanger 207, thereby producing cold second reflux stream 213, which is introduced into LP column 202.

LP column 202 produces at least three output streams, liquid oxygen stream 214, cold waste nitrogen stream 215, and cold gaseous nitrogen stream 216. Liquid oxygen stream 214 passes through first heat exchanger 203, thereby producing gaseous oxygen product stream 115. Gaseous oxygen product stream 115 may have a pressure between 1.1 and 3 bara, preferably between 1.2 and 2 bara. Cold waste nitrogen stream 215 passes through second heat exchanger 207, thereby producing waste nitrogen stream 113. Cold gaseous nitrogen stream 216 passes through second heat exchanger 207, thereby producing gaseous nitrogen product stream 111.

Gaseous nitrogen product stream 111 is introduced into main heat exchanger 104, thereby producing warmed gaseous nitrogen product 112. Waste nitrogen product stream 113 is introduced into main heat exchanger 104, thereby producing warmed waste nitrogen product 114. Gaseous oxygen product stream 115 is introduced into main heat exchanger 104, thereby producing warmed gaseous oxygen product 116.

HP gaseous nitrogen stream 117 is introduced into main heat exchanger 104, thereby producing warmed HP gaseous nitrogen stream 118. Warmed HP gaseous nitrogen stream 118 is then introduced into turboexpander 119, thereby producing LP gaseous nitrogen stream 120. LP gaseous nitrogen stream 120 is then introduced into main heat exchanger 104 thereby producing warmed LP gaseous nitrogen stream 121. Second booster air compressor 302 and turboexpander 119 may be connected with a common drive 303.

In another embodiment, as illustrated in FIG. 7 and FIG. 8 , HP column 201 produces at least 3 output streams rich liquid stream 208, nitrogen reflux stream 212, and HP gaseous nitrogen stream 117. Rich liquid stream 208 passes through second heat exchanger 207, thereby producing cold rich liquid stream 209, which is introduced into LP column 202. Nitrogen reflux stream 212 passes through second heat exchanger 207, thereby producing cold reflux stream 213, which is introduced into LP column 202.

LP column 202 produces at least two output streams, liquid oxygen stream 214, cold waste nitrogen stream 215, Liquid oxygen stream 214 passes through first heat exchanger 203, thereby producing gaseous oxygen product stream 115. Gaseous oxygen product stream 115 may have a pressure between 1.1 and 3 bara, preferably between 1.2 and 2 bara. Cold waste nitrogen stream 215 passes through second heat exchanger 207, thereby producing waste nitrogen stream 113. Waste nitrogen product stream 113 is introduced into main heat exchanger 104, thereby producing warmed waste nitrogen product 114. Gaseous oxygen product stream 115 is introduced into main heat exchanger 104, thereby producing warmed gaseous oxygen product 116.

HP gaseous nitrogen stream 117 is introduced into main heat exchanger 104, thereby producing warmed HP gaseous nitrogen stream 118. Warmed HP gaseous nitrogen stream 118 is then introduced into turboexpander 119, thereby producing LP gaseous nitrogen stream 120. Turboexpander 119 may have an inlet pressure of between 4 and 10 bara, and an outlet pressure of between atmospheric pressure and 2 bara. Turboexpander 119 may have a loading or braking device to act as a sink for the expander's energy. As a brake, turboexpander 119 may utilize a booster, a generator or oil (not shown). Typically, a booster brake is preferred to put as much energy back into the system as possible, with less overall losses and equipment cost. LP gaseous nitrogen stream 120 is then introduced into main heat exchanger 104 thereby producing warmed LP gaseous nitrogen stream 121. Second booster air compressor 302 and turboexpander 119 may be connected with a common drive 303.

It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims, Thus, the present invention is not intended to be limited to the specific embodiments in the examples given above. 

What is claimed is:
 1. An air separation process comprising: a first booster air compressor comprising a first outlet stream, a second booster air compressor comprising a second outlet stream wherein the first booster air compressor and the second booster air compressor are in parallel, and wherein the second booster air compressor is driven by a nitrogen turboexpander.
 2. The air separation process of claim 1, wherein the first outlet stream and the second outlet stream are combined and introduced into a common after-cooler.
 3. The air separation process of claim 1, wherein the first booster air compressor has a first inlet pressure and the second booster air compressor has a second inlet pressure, and wherein the first inlet pressure and the second inlet pressure are within 1 bar.
 4. The air separation process of claim 1, wherein the first booster air compressor has a first outlet pressure and the second booster air compressor has a second outlet pressure, and wherein the first outlet pressure and the second outlet pressure are within 1 bar.
 5. The air separation process of claim 1, wherein the nitrogen turboexpander has an inlet pressure in the range of 4 to 10 bara and outlet pressure in the range of atmospheric pressure to 2 bara.
 6. An air separation process producing low pressure gaseous oxygen comprising: a first booster air compressor comprising a first outlet stream, a second booster air compressor comprising a second outlet stream wherein the first booster air compressor and the second booster air compressor are in parallel, wherein the second booster air compressor is driven by a nitrogen turboexpander, wherein, the first outlet stream and/or the second outlet stream is at least partially condensed by heat exchange with a vaporizing low pressure oxygen stream, and wherein the low-pressure gaseous oxygen pressure is in the range of 1.1 bara to 3 bara.
 7. The air separation process of claim 6, wherein the first outlet stream and the second outlet stream are combined and introduced into a common after-cooler.
 8. The air separation process of claim 6, wherein the first booster air compressor has a first inlet pressure and the second booster air compressor has a second inlet pressure, and wherein the first inlet pressure and the second inlet pressure are within 1 bar.
 9. The air separation process of claim 6, wherein the first booster air compressor has a first outlet pressure and the second booster air compressor has a second outlet pressure, and wherein the first outlet pressure and the second outlet pressure are within 1 bar.
 10. The air separation process of claim 6, wherein the nitrogen turboexpander has an inlet pressure in the range of 4 to 10 bara and outlet pressure in the range of atmospheric pressure to 2 bara.
 11. air separation process of claim 6, wherein the low-pressure gaseous oxygen pressure is in the range of 1.2 bara and 2 bara.
 12. The air separation process of claim 6, wherein the first outlet stream and the second outlet stream are combined, and the combined stream is at least partially condensed by heat exchange with a vaporizing low pressure oxygen stream. 